Well, as work caught up with me I missed the Lisbon experience, but apparently it was raining there anyway - so it was just like home!
As I mentioned profiles in my last blog, I thought I would expand on these based on Andrew Josey's presentation [PDF from Open Group Site] to see what they look like and how they might apply to RTOSes (such as VxWorks), Linux and DSO in general. (He has an excellent diagram on Page 18 that shows the POSIX standards evolution....)
PSE51 or Minimal has 287 APIs and is aimed at small embedded system, with no MMU, no disk, no terminal
PSE52 or Realtime Controller has 626 APIs and is aimed at special purpose controllers, again with no MMU, but with a disk containing a simplified file system
PSE53 or Dedicated has 754 APIs and is aimed at large embedded system with file system on disk, with an MMU; software is complex and requires memory protection and network communications
PSE54 or Multi-Purpose has 912 APIs and is aimed at large real-time system with all the features,
including a development environment, network communications, file system on disk, terminal and
graphical user interfaces, etc.
Now you also find that even these are not enough and you get subsets of these such as the SCA 2.2.2 which defines a subset of PSE52 with 267 API calls. This API is also most likely to be one used in Safety Critical Systems as the SCA is required for this under JTRS.
So, the theory goes you would pick the correct subset based on the type of application you are building. And in fact I think the theory works well; say you build a small standalone system dedicated to single function using PSE 52, then as systems merge and performance increases you want to merge that onto a larger system the application can be "easily" ported to a PSE 54 system.
Of course, the question still remains as to whether the PSE 54 system has the Real Time capabilities you need to execute your code correctly, and that the PSE 54 system you port to is as conformant as your PSE 52 system, but that's what the conformance tests Andrew Josey presents are all about, right?
Alex Wilson is a Senior Program Manager with Wind River in the UK, working with Aerospace and Defence customers across EMEA. In this role, Alex has the opportunity to meet with A&D customers and partners across EMEA and help define the A&D Strategy at Wind River.
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